James b



(No Model.)

J. B. ALLPREE.

GRINDING ROLL.

No. 362,196. Patnted May a, 1887.

FIGJ.

FIGA.

UNITED STATES PATENT OFFICE.

JAMES B. ALLFREE, OF CUMBERLAND, MARYLAND, ASSIGNOR OF ONE-HALF TO ROBERT SHRIVER AND HARRISON SWARTZW'ELDER, BOTH OF SAME PLACE.

GRlNDlNC-Q-ROLL.

SPECIFICATION forming part of Letters Patent No. 362,196, dated May 3, 1887.

Application filed January 5,1886. Serial No. 187,680. (No model.)

To all whom it may concern.-

Be it known that 1, JAMES B. ALLFREE, a citizen of the United States, residing at Cumbe'rland, Maryland, have invented new and useful Improvements in Grinding-Rolls, of

which the following is a specification.

This invention relates to rolls employed in. roller grinding-mills, and particularly to the form of the corrugations or ribs upon their IO operative surfaces.

The great desideratum in rolls of this kind is to provide the same with operative surfaces having corrugations of such form that by changing the relative positions of the rolls and changing the speed of each, independent of the other, an action may be produced upon the material varying from a very sharp cutting action to an exceedingly dull noncutting but crushing action, to suit the various quali- 2o ties of material to be acted upon; andthe object of the present invention is to produce rolls possessing these characteristics.

\Vith this object in view the invention consists of a roll for use in roller grinding-mills provided with teeth orcorrugations trending lengthwise of the roll, the whole operatingsurface of each tooth being of such contour as is formed by the meeting of two simple reversed curves at an obtuse angle, one side thereof being concave and the other convex.

In order that those skilled in the art to which my'invention relates may know how to make and use the same, I will now proceed to describe the particular form of corrugations em- 5 ployed and the various effects which may be produced upon the material therewith, in connection witlrthe accompanying drawings, in which- Figure 1 represents a small portion of the 40 contiguous grinding-surfaces of a pair of rolls so arranged and speeded as to exercise asharp cutting action upon the material. Fig. 2 is a similar view indicating the arrangement and speed employed to perform a cutting action 5 in a degree less severe than that done by the arrangement shown in Fig. 1. Fig. 3 shows the arrangement and speed used when a less severe action than that performed by the arrangement shown in Fig. 2 is employed, and

Fig. 4 shows the arrangement employed to perform a dull crushing reduction.

In the drawings, A represents the longitudinal teeth or flutes, which are placed upon the rolls and extend from end to end thereof, and are arranged either parallel or slightly spiral 5 5 to the axis of the rolls. The number of flutes per inch formed upon the rolls varies from twelve to thirty-two, according to the class of work to be performed.

The rolls are mounted in suitable frames, and are so arranged that they may be turned end for end, and may be capable of having their speeds increased or decreased independ ent of each other. The means for accomplishing this forms no part of the present invention, however, and need not therefore be per ticularly described here.

The corrugations are, as will be apparent from an inspection of the drawings, of such contour that the whole or entire operative surface of each tooth or corrugation is the same as is formed by the meeting of two reversed curves at an obtuse angle, which curves, if continued or extended, would describe two circles having their centers at opposite equidistant points from the angles of intersection, and one side of said corrugations is concave, while the other is convex. This form produces upon the convex face a very dull grinding-surface, while the crest of the rib upon the concave side is exceedingly sharp. Thus it will be apparent that when the rolls are arranged as shown in Fig. 1, and the roll 1 run at a higher rate of speed than roll 2, the sharp crests will be brought into action upon the ma- '8 5 terial and an exceedingly sharp cutting action exercised. When a less severe cutting action than that exercised by the arrangement shown in Fig. 1 is required, the rolls are so arranged that the dull or convex sides of the flutes of 0 the fast roll shall come in contact with the sharp or concave sides of the flutes of the slow roll, as shown in Fig. 2. I

In Fig. 3 the rolls are so arranged that the sharp or concave sides of the flutes of the fast roll shall come in contact with the dull or convex surfaces of the slow roll, and this arrangement produces a less severe action than that produced by the arrangement shown in Fi 2. When a dull absolutely noircutting action is required, the parts are arranged in the same Way as in Fig. 1, and roll No. 2 is run at a higher rate of speed than rolll. This brings the dull surfaces of both rolls in contact, as will be seen from an inspection of Fig. 4:.

From this description it will be apparent that any action varying from an exceedingly sharp cutting action to an equally dull non-cutting action may be secured, and the rolls there fore adapted to any ordinary class of material.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. A roll for roller grinding-mills provided with ribs or corrugations of such contour asis formed by the meeting of two simple reversed curves at an obtuse angle, one side of the said ribs being concave and the other convex, sub- 

